SS7 networks have long been employed to carry critical data pertaining to the management of telecommunication networks, such management includes, for example, setting up and tearing down communication sessions as well as the provision of intelligent services. These intelligent services include, for example, 800 number calling, calling card services, cellular phone roaming, and the like. To facilitate discussion, FIG. 1 is a prior art diagram of a typical SS7 network 102, including a plurality of Signaling Transfer Points (STPs) 104, 106, 108, 110, 112. As is well known, a STP functions as a packet switch for SS7 messages. The STPs are interconnected in a mesh network in pairs for redundancy, with the STPs of each pair being identical.
External communication nodes gain access to the SS7 network by connecting to a pair of STPs. For example, switches 120, 122, and 124 gain access to SS7 network 102 by connecting to the pair of STPs 112 and 114 as shown. A Signaling Control Point (SCP) 130 is also shown in the example of FIG. 1. SCP represents a node that contains a service database and application to provide, for example, the aforementioned intelligent services. For example, if a user of a telephone 170 dials an 800 number (e.g., 1-800-123-4567), the routing information for that 800-number call is provided by SCP 130 since the 800 number service involves a virtual telephone number. In this case, switch 120 sends a message to SCP 130 to ask for routing instructions to enable the 800-number call to be set up.
When the SS7 network was originally conceived, the speed of the links between the STPs in the mesh network were relatively slow, typically on the order of 56 Kbits/second. As the network grows, more external communication nodes such as switches are connected to the network. Accordingly, it is not unusual for a STP pair to be connected to tens or hundreds of switches, for example, as the network grows. Since each STP acts as a concentration point into the SS7 network for all the SS7 messages to and from all the external nodes connected to it, the traffic between STPs on the mesh network increases correspondingly over time. Thus as the network grows, the low-speed links between the STPs of the mesh network become a bottleneck to network performance.
Increasing the number of links between STPs represents one approach to solving the SS7 network bandwidth bottleneck problem. However, the SS7 standard places a limit of 16 links between any two nodes (e.g., any two STPs). Consequently, once the limit of 16 links is reached between pairs of STPs, the other way to relieve the bandwidth bottleneck in the SS7 network is to increase the speed of the links.
High Speed Link (HSL) represents one technology that has been adopted by many SS7 network operators for high speed transmission in the SS7 network. The guiding documentation for implementing HSL may be obtained from Telcordia (previously BellCore), and/or ANSI/ITU-T standards. HSL transports SS7 messages over ATM (Asynchronous Transfer Mode) cells employing T1 connections. As is well known, a standard T1 connection supports 24 56-Kbits/second links. However, due to the inefficiency involved in transporting SS7 messages over ATM cells, the actual throughput is on the order of 14 56-Kbits links. In other words, a high overhead penalty is imposed with the use of HSL. However, HSL still offers significantly better performance than the previous 56 Kbits link speed. Consequently, HSL is deemed an acceptable solution for relieving the bandwidth bottleneck among the STPs.
The same bandwidth bottleneck also exists with regards to the links between SCP 130 and the SS7 network, e.g., on links 170 and 172 between SCP 130 and STPs 104 and 106 of the SS7 network. Not surprisingly, as more external communication nodes are connected to the SS7 network and as intelligent services become increasingly popular among telecommunication users, more traffic is sent to and from the SCPs. Again, once the number of links to and from a SCP reaches 32, the other way to increase data throughput to and from a SCP is to increase the speed of the links themselves. Solving this bandwidth bottleneck is also critical for network performance.
While HSL has been a satisfactory interim solution for increasing the transmission speed between STPs in the SS7 network, integrating HSL into the SCPs has proven to be more expensive and difficult than anticipated. In the era of cost-cutting, service providers and network operators chaff at the high development cost involved in such integration, and HSL has not gained acceptance for SCP-to-STP communication in the same way that it has for STP-to-STP communication.
Another approach is to employ a relatively new technology called SS7-over-IP to carry data between the SCPs and the SS7 network. SS7-over IP involves carrying SS7 messages over IP (Internet Protocol) packets and has the potential for very high speeds, e.g., 10 Mbits/second, 100 Mbits/second, or even greater. In fact, some SCPs have developed the capability for transmitting SS7 messages using SS7-over-IP in anticipation of the SS7 network evolution to IP networks. While this may be the ultimate solution for future networks, the proposal to use SS7-over-IP as the transmission technology between a SCP and the SS7 network has not been widely accepted by today's cost-conscious and highly conservative network operators. For one, existing STPs are configured to communicate using HSL, and network operators are highly reluctant to perform the upgrade to enable STPs to communicate using SS7-over-IP, as an alternative or in addition to HSL.
Furthermore, existing SS7 network operators tend to associate IP with lossy transmission and tend to perceive IP to be an unreliable technology for the transmission of critical data, such as SS7 messages. The other considerations are more political but also impact the acceptance of SS7-over-IP by SS7 network operators. SS7 administrators loath to surrender control of their “mission-critical” SS7 networks to IP administrators, who are deemed to be concerned with the maintenance of a lossy IP network geared toward transporting low-priority, non-mission-critical data. SS7 network operators also prefer to keep the transmission of SS7 messages within a dedicated private physical network instead of a public network, such as networks implementing IP.
Accordingly, a new solution is desired to relieve the bandwidth bottleneck between the SCPs and the SS7 network.